Eugene is in prison where "Chess Man" gambles cigarettes with him over chess games. When Eugene is ready to be released he confides that he is concerned about not having many friends on the outside any more. He receives a wooden king chess piece from Chess Man and is told "Take care of the King, everything else follows". On the outside Eugene looks for work and has trouble finding it due to his ex-con status. He attempts to reconnect with his daughter Katrina (Trini) who rebuffs his attempts but informs him that his son Marco is in Juvenile Hall for selling drugs. His friend Billy connects him with a job at a local high school working as a janitor. Eugene gets a visit from his former lieutenant Perry who is now prosperous and the man in charge. The lure to return to his former ways is strong. At the local high school, the students are unruly and dealing drugs in detention and scare off the detention monitor. The principal Sheila King asks Eugene to fill in as detention monitor for a few minutes. He proves to be unexpectedly persuasive at getting the students to sit down and follow the rules. He is allowed to return as the detention monitor until a replacement can be found. Eugene bets on a game of cards with a student and wins, the prize being that the students will learn to play chess.

Two of the students Tahime Sanders and Clifton are dealing drugs and contemplating armed robbery. Eugene draws a parallel comparing Clifton to a pawn working for a king he calls refers to as "King Perry". Clifton tells Perry that Eugene is running detention and preventing the sell of weed there, leading to reduced profits for Perry. Tahime proves to be an excellent strategist on the Chess board. Tahime invites another student (Peanut) in on the crimes they are engaged in. The principal receives an anonymous tip (from Perry) that Eugene is an ex-con and she is forced to fire him.

Eugene visits Perry who offers him cash. Mean Gene does not accept the money and walks away. Eugene attempts to restart the chess club by driving to the local hang out joint for the teenagers, but they refuse to play outside of detention. Peanut changes his mind and goes with Eugene who makes him president of the chess club by giving him the wooden king piece. Eugene rents a run down house in Washington D.C. for the chess club. Clifton and Tahime come to the chess house to get Peanut and take him to rip off some dealers. Peanut is shot and killed in the course of the robbery. While Eugene goes to comfort Tahime the chess house is vandalized.

Tahime refuses to stay involved with Clifton. He comes back to the Chess house and returns the wooden king piece he got from Peanut's body. The chess team regroups and restores the house and begins advertising via flyers around town and around the school. Eugene convinces Tahime to compete in a chess tournament, but Tahime's mother refuses to sign the consent form. He forges her signature and enters the contest. Tahime wins the tournament, however, the officials disqualify the team due to the forged signature and the lack of birth certificates for the students (despite Eugene saying some of the students don't have birth certificates "where we come from"). A local radio producer invites Eugene and Tahime to come on the air and present their argument. Eugene presents his view that they didn't win, because they didn't play by the rules, and that is crucial in his view (learning the rules and winning within them). Tahime is angered by this line of reasoning and storms off. While looking for Tahime, Eugene fails to accompany his daughter to get his son Marco, which leads to anger between them.

Tahime returns and wants to play in the Washington D.C. chess open tournament. He begins to study chess from a book and practice relentlessly. Clifton is arrested and calls Perry from Prison, but is hung up on (illustrating his role as a pawn). Tahime advances to the final match and faces one of the best players in the country, J. Thomas Gaines. Tahime puts up a good fight but ultimately loses. Nonetheless, Tahime gets a standing ovation from his supporters in the crowd. A representative of the Urban League gives her card to Eugene, saying she wishes to help him go to college. Gaines tells Tahime that "that was the first time I've been scared all year."

Life of a King received mixed reviews from critics. Review aggregation website Metacritic gives a rating of 52 out of 100 based on reviews from seven critics, which indicates "mixed or average" reviews. The review aggregator website Rotten Tomatoes reported a 38% approval rating with an average rating of 5.3/10 based on 13 reviews.